Air-speed indicating system for rotary winged aircraft



E. A. LINK AIR-SPEED INDICATING SYSTEM FOR ROTARY WINGED AIRCRAFT Nov.28, 1950 2 Sheets-Sheet 1 Filed Oct. 16, 1943 EDWIN A. UNK.

BYW I fl//p/f/fl/g ATTORNEYS.

E. A. LINK AIR-SPEED INDICATING SYSTEM FOR ROTARY WINGED AIRCRAFT Nov.28, 1950 2 Sheets-Sheet 2 Filed Oct. 16, 1945 FIG. 3

EDWIN A. LINK INVENTOR.

ATTORNEYS.

Patented Nov. 28, 1950 UNITED STATES PATENT OFFICE 2,531,521 AIR-greeniNpioA'rINGSYsTEM i oi't ROTARY WIN GED AIRCRAFT Edwin A. Link,Binghamto'n, N. Y.

Application October 16, 1943, Serial No. 506,461

' 2 Claims.

My invention relates to an air speed indicator for rotary wingedaircraft.

One of the basic instruments used in th navigation of aircraft is theair speed indicator which indicates the forward speed of the craftthrough the mass of air in which it is flying. Such an indicatorcomprises a Pitot tube and a static tube, the former being responsive toth impact pressure of the air caused by the travel of the plane throughthe air while the latter is responsive to the static pressure of the airsurrounding it. These two pressures are introduced. into the air speedindicator which comprises well known mechanism for indicating, accordingto the relative values of the pressures, the air speed of the vehicle inquestion. However, an air speed indicator will function satisfactorilyonly in case the Pitot and static tubes are placed at a point upon thecraft where the air is undisturbed by either the forward travel of thevehicle or by the action of its propeller. For this reason the tubes, inthe case of an airplane, are usually placed on the leading edge of oneof its wings at a point transversely removed from the propeller orpropellers, or in the event the nose of the plane is substantially aheador the proing them which causes the helicopter to travel vertically,forward, backward and sideways. The action of the blades upon the airresults in the movement downward therefrom of a turbulent column of airwhich practically completely engulfs the whole fuselage and attachedparts, and therefore, experts in the field have beenunable to locate anypoint upon the helicopter at which the Pitot and static tubes maybe'placed to give satisfactory air speed indications.

It is therefore the principal object of my invention to provide means bywhich the air speed of a rotary winged aircraft or helicopter may besatisfactorily determined. a

It is a related object of my invention to pro-' vide means by which theusual Pitot and static tubes may be combined with a modified conven-'tional air speed indicator to indicate .the air speed of such anaircraft.

It is a further object of my invention to pro-'1 sures at the end of therotary wings may be measured when the end of the wing is movingsubstantially parallel to the line of flight, to position an element inaccordance with these pressures, and then to combine with thepositioning of this element a factor representative of the speed throughthe air of the Pitot and static tubes caused by the rotation of thewings, whereby the final indicated result is that of the speed throughth air of the Pitot and static tubes caused by the travel of theaircraft through the air.

In order that my invention may be more readily understood reference ismade to the accompanying drawings in which a preferred embodiment of myinvention is shown in combination with a helicopter. In the drawings,

Fig. l is a general view of a helicopter showing Pitot and static tubespositioned at the end of one of the wings attached to the main rotor.

Fig. 2 shows the hub of th rotor modified in accordance with myinvention.

Fig. 3 is a view of an air speed indicator modified to meet the purposesof my invention.

Reference is now made to Fig. 1 which shows the general View of ahelicopter and in which the number it designates the fuselage to whichsuit-' able landing gear I2 is attached. The main rotor 84 has its lowerend (not shown) suitably mounted in the fuselage, while surrounding thisrotor is member It which will later be described in detail. Hub I8 isfixedly attached to the upper end of rotor 14 and fixed thereto forrotation therewith are a plurality of shafts 2E, each of which carries awin'g 22. Mounted upon the end of one or more of the wings 22 is a Pitottube 24 and a static tube 26. I so position the Pitot 28 which is usedto steer thevehicle in a Well known manner.

Reference is now made to Fig. 2 showing hub [8 which is rigidly affixedto rotor l4 and member l6 which surrounds rotor it but does not turntherewith. A plurality of bores 532 and 3d are placed in hub l8, andeach of the tubes 35 connects with one of the bores 32 While a similartube 38 connectsw'ith each of the bores 34. These tubes are preferablywithin the shafts 29 which support wings 22, and the other end of eachof the tubes 36 connects with a Pitot tube 24 mounted upon the end ofone of the wings 22 while the other end of each of the tubes 36 connectswith a static tube 26 also mounted upon the end of one of the wings 22.It should be noticed that for each wing 22 that has a Pitot and statictube mounted thereupon there are a pair of tubes 36 and 38 and a pair ofbores 32 and 34.

In member I6 is a pair of bores 49 and 42 and in communication with thebore 49 is a tube 420., the other end of which terminates insidediaphragm 42b, which, as shown in Fig. 3, is within airtight casing 44which houses the mechanism of my modified air speed indicator.Similarly, in communication with the bore 42 is a tube 46, the other endof each of which terminates inside casing 44 outside diaphragm 42b.

Bores 49 and bores 42 are positioned within fixed member I6 so that theyare in communication with each pair of bores 32 and 34 only when thePitot and static tubes 24 and 26 connected to the tubes 36 and 38 aretraveling in a path substantially parallel to the line of flight of thehelicopter and, therefore, intermittently, a pressure proportional tothe speed through the air of the ends of the wings 22 is introducedinside diaphragm 421) while the static pressure existent at the sameinstant is introduced inside casing 44 and outside diaphragm 42b.Inasmuch as the Pitot pressure exceeds the static pressure by an amountproportional to the rate of travel of,.the Pitot and static tubes 24 and26 at the instant when bores 32 and 34 are in communication with thebores 49 and 42, diaphragm 42b will expand proportionately, raisingbracket 48 which is rigidly mounted upon the upper movable surface ofthe diaphragm. Arm 59 will have its end resting upon bracket 48 raisedand inasmuch as its other end is fixedly attached to rocker arm 52 whichhas each of its ends pivotally mounted within casing 44, rocker arm 52will be rotated counterclockwise as seen from the left side in Fig. 3.Vertical shaft 54 which has its lower end afi'ixed to rocker shaft 52will therefore move toward the rear of the instrument as seen in Fig. 3,carrying before its upper end the arm 56 against which it bears. Arm 56has its rightmost end aifixed to yoke 58 which is pivotally mounted bymeans of pin 69 to airtight sealing disc 62 within casing 44. Theresulting movement of arm 56, it will be understood, will carry yoke 58with it, and the gear sector 64 formed integrally with this yoke willmove therewith.

Sector 64 is in mesh with pinion 66 fixedly mounted upon vertical shaft68 to the lower end of which the inside end of anti-back lash torsionspring I9 is attached. The outer end of this spring is anchored tobracket I2 which is attached to the inside of casing 44. The lower endof vertical shaft 68 is held by a bracket (not shown) also attached tothe inside of casing 44.

Vertical shaft 68 passes through disc 62 by means of an airtight fittingand is directly connected to bevel gear I4 which is the primary drive ofdifferential designated generally by I6. This diiferential comprisesthree other bevel gears combined within yoke I8 in a well-known manner.Another vertical shaft 89 is affixed to the uppermost of these bevelgears 82 for rotation therewith, and attached to the upper end of thisshaft is pointer 84 which moves over dial 86 which is calibrated,preferably, in miles per hour.

From the foregoing it will be realized that the expansion of diaphragm42b which moves gear sector 64 toward the rear of the instrument casing44 as seen in Fig. 3 will cause a counterclockwise rotation of pinion66, as seen from above, and a similar rotation of vertical shaft 68 andbevel gear I4 will occur. Bevel gears 88 will rotate in such a directionto cause bevel gear 82 to rotate clockwise, as seen from above, andvertical shaft 89 will turn in the same direction, carrying with itpointer 84 over scale 86. Inasmuch as the expansion of diaphragm 42b isproportional to the rate of travel of the Pitot and static tubes '24 and26 through the surrounding air, which rate of travel is the forwardspeed of the craft through the air plus the rotary speed of the wings22, it will be understood that in the absence of any modifying mechanismpointer 84 and dial 86 will indicate the air speed of the helicopterplus the rate of travel of the ends of the wings through the air. Meanswill now be described whereby the factor of rotary rate of travel of theends of the wings 22 through the air may be subtracted from this sum offorward speed of the helicopter through the air plus rotary speed of theends of the wings, whereupon pointer 84 and dial 86 will indicate theforward speed of travel through the air of the craft.

Seen inFig. 3 is a shaft 99 which is connected to rotor I4 in a mannerthat its speed of rotation will be proportional to the speed of rotationof this rotor. This shaft has one end which projects inside casing 44above disc 62 and fixedly mounted upon its interior end is spur gear 92which is in mesh with pinion 94 formed integrally with horizontal shaft96 rotatably mounted within casing 44. Fixedly attached to the left endof shaft 96 by means of pin 98 is collar I99 which in turn has two armsI92 pivotally attached thereto as shown, the other end of each of thesearms being likewise attached to a weight I94. Another pair of arms I96have their left ends pivotally attached to weights I94 while their otherends are similarly attached to collar I98 which is slidably mounted uponshaft 96. Compression spring 9! surrounds shaft 96 and bears againstcollars I99 and I98. Fixedly attached to collar I98 is depending arm H9whose lower end engages arm H2 fixed to yoke H4 which is pivotallymounted upon disc 62 by means of pin H6. Formed integrally with yoke II4 is sector gear I I9 which is in mesh with spur gear I29 which isaffixed to yoke I8 of differential I6, thus forming a secondary drivefor this differential. It will be realized that a rotation of gear I29will turn yoke I8, and inasmuch as bevel gear I4 is prevented fromturning by gear 66 and sector 64, bevel gears 88 are rotated causing arotation of bevel gear 82 and vertical shaft 89, and pointer 84 movesover dial 86. The faster the rotation of shaft 99, which rotation itwill be recalled is proportional to the speed of rotor I4, the greaterwill be the speed of rotation of shaft 96. Weights I94 will therefore bethrown a greater distance from shaft 96, and collar I98 will be moved tothe left in Fig. 3 against the action of spring 91 carrying with it armI I9, the lower end of which will move arm H2 and yoke H4 to which it isattached clockwise as seen from above. Gear sector H8 will thereforemove in the same direction and spur gear I29 will be movedcounterclockwise as seen from above, thereby turning yoke I8 ofdifferential I6 in the same direction. Bevel gear I4 remains stationary,but bevel gears 88 are turned in such a direction to rotate bevel gear82 counterclockwise as seen from above, Vertical shaft 89 is turned inthe same direction, and pointer 84 moves counterclockwise over dial 86.Inasmuch as dial 86 is graduated to indicate a higher airspeed aspointer 84 moves clockwise over dial 86, the counterclockwise rotationof pointer 84 caused by an increase in the rate of rotation of rotor [4will be subtracted from the primary clockwise rotation of pointer 84caused by an increase in the rate of rotation of rotor [4.

From the foregoing it should be understood that my airspeed indicatorfor rotary Winged aircraft comprises, generally, means for measuring thePitot and static pressures at a point along one or more of the rotatingwings when the wing is traveling along a path substantially parallel tothe line of flight, positioning an element in accordance with the saidpressures, and then modifying the position of said element in accordancewith the rotary speed of the blade, whereupon the final position of saidelement is indicative of the air speed of the craft.

Iclaim:

1. An airspeed indicating system for a rotary winged aircraft comprisingdynamic and static pressure intakes on a wing of the aircraft, a valveconnected to the intakes and dynamicstatic pressure responsive meansconnected to the valve, means to actuate said valve in synchronism withthe rotation of the wing to connect said intakes to said dynamic-staticpressure re- REFERENCES CITED The following references are of record inthe file of this patent:

UNITED STATES PATENTS Number Name Date 652,666 Darlington June 26, 19001,146,202 Ogilvie July 13, 1915 1,525,963 Sperry Feb. 10, 1925 2,209,879Focke July 30, 1940 2,210,388 Vail Aug. 6, 1940 FOREIGN PATENTS NumberCountry Date 372,204 Great Britain May 5, 1932

